The goal of this K99/R00 proposal is to develop a new translational research framework whereby the role of the mechanical properties in tumor growth and molecular response are specifically exploited to design new photodynamic therapy (PDT) combination treatments for pancreatic cancer. Previous studies have shown that while the rigidity of the extracellular matrix surrounding cells directly impacts growth, development and signaling, the relevance of this crucial factor to treatment response has not yet been explored. This is particularly relevant for tumors of the pancreas which are characterized by a profound growth of dense fibrous tissue around the tumor (called desomplasia). In order to overcome this limitation in our scientific knowledge, this proposal introduces a highly interdisciplinary approach combining 1) fluorescence laser tracking microrheometry (FLTM) a novel optical technology to measure the mechanical properties (microrheology) in and around tumors, 2) a customizable three-dimensional (3D) tumor model system using a synthetic nanofiber scaffold called PuraMatrix with tunable matrix mechanics, 3) a high-throughput quantitative imaging approach to report tumor growth properties and treatment response in relation to matrix mechanical properties. Dr. Celli will first optimize the 3D model system informed by studies on ex vivo tumors from orthotopic PanCa mice, to assess the impact of matrix rheology (measured by FLTM and traditional bulk rheology) on growth and development of 3D in vitro tumors. He will conduct PDT treatments and specific survival factors as potential targets for mechanism based combination treatments that are customized to each synthetic mechanical microenvironment. He will then evaluate the efficacy of the most promising combination treatments to test the hypothesis that only a treatment customized for the appropriate mechanical microenvironment will in fact achieve a synergistically enhanced efficacy in that environment. The research will culminate in testing of the most promising strategies in a mouse model of pancreatic cancer. If successful, this research will not only produce urgently needed new treatments for a deadly disease, but will also add a new level of understanding to guide the design of future treatments which could be applied to the study of other tumors. A mentoring committee has been assembled to guide the research in the K99 phase and facilitate Dr. Celli's training. Dr. Tayyaba Hasan, who is an expert in PDT treatment of cancer will provide primary mentorship and guidance in the overall study design. Co-Mentor, Dr. Peter So is a world expert in novel imaging technologies. He will guide Dr. Celli in FLTM measurements (which was developed in his laboratory) and help interpret results. Training in the molecular biology and treatment of pancreatic cancer will be provided by Dr. Nabeel Bardeesy and Dr. Stephen Pereira. Dr. Gareth McKinley will provide additional mentorship in rheology and microrheology. The opportunities provided by this award will not only allow Dr. Celli to pursue potentially ground-breaking research, but will also provide him with valuable mentorship and training to his career as an independent investigator.